1. Field of the Invention
The present invention relates to a thermal transfer recording material and a thermal transfer recording method
2. Description of Related Art
Conventionally, color image recording by inkjet, electrophotography, thermal transfer, silver halide photosensitive materials and the like has been studied as methods for obtaining color hard copies. Among them, the image recording using a thermal transfer recording material has advantages such as easy operation and maintenance, downsized apparatus, potential reduction in cost and further inexpensive running cost.
In the image recording using this thermal transfer recording material, a colorant used for the thermal transfer recording material (also referred to as a thermal transfer material) is important. For the purpose of improving stability, particularly fixable property and light resistance of an image obtained, thermal transfer recording materials using thermally diffusible colorants (referred to as post-chelate colorants) capable of being chelated and a image forming method, i.e. thermal transfer recording methods, have been proposed, and described in, for example, JP SHO 59-78893 A, JP SHO 59-109349 A and JP SHO 60-2398 A. An image formed using the post-chelate colorant shown in the above documents is excellent in light resistance and fixable property, but is not sufficiently satisfied in sensitivity of the thermal transfer material and storage stability of the material itself. Furthermore, since a hue difference between the post-chelate colorant and the metal chelate colorant is large, when a chelate reaction is insufficient upon the image formation, absorption of the unreacted post-chelate colorant remains, or the formed metal chelate colorant itself is irregularly absorbed. Therefore, when a full color image is obtained, it has been necessary to further improve color reproducibility.
Thus, in JP HEI 3-143684 A, JP HEI 3-143686 A, Tokugan Hei 9-257947, and Tokugan Hei 11-60123, the thermal transfer recording materials using the colorants having pyrazolopyrimidine-7-one center nuclei have been proposed. In these colorants, problematic points as the above are improved to some extent, but the improvement is not sufficient, and in particular, the storage stability (heat and humidity resistance) under a high temperature and humidity condition and the storage stability under light irradiation (light resistance) are insufficient. Therefore, further improvement has been desired.
Furthermore recently, for responding to speeding up of image printing, it is regarded as important to express dark and light with lower energy. That is, with respect to the colorant, the colorant with high heat responsibility, i.e., high sensitivity has been desired earnestly. However, including a balance with the storage stability, the above colorants do not reach a sufficient level yet.